Historically, the badger was a fairly common species in the Naliboki Forest, located in the north‑western part of Belarus. According to information obtained from residents, who were familiar with the forest in the 1930s–1960s (e.g., Baliaslaw Sadowski, Lianard Jurevich, Edzik Khmara), badger setts were widespread. Approximately, the density of main setts – those used by family groups for overwintering, giving birth and raising cubs – was not lower than 15 per 100 km² in the most ecologically rich southern part of the forest, and about 4 per 100 km² in the central and central‑northern parts, where habitat carrying capacity for badgers is markedly lower. This suggests that the former density of a more or less undisturbed badger population in Naliboki Forest ranged roughly between 20 and 120 individuals per 100 km², depending on habitat quality.
Excessive rate of illegal hunting that happened in the 1970s was evaluated as the main cause of badger decline in the whole Belarus (Daraphieyew et al., 1981), but seemingly there were other significant causes for the decline in badgers.
In summer 2007 in Naliboki Forest we censused seven active setts on the area of 690 km2, i.e. 1 active sett per 100 km2 and 2.6 inds per km2. In the seven active setts found we revealed the following inhabitants: (1) 3 adults, 1 subadult, 2 cubs; (2) 1 adult; (3) 1 adult; (4) 1 adult; (5) 3 adults; (6) 2 adults, 2 cubs; (7) 2 adults. Only two out of seven active setts held litters (28.6 %). Approximate portion of juveniles was 22.2 %.
In summer 2008 in Naliboki Forest we censused again 7 active setts on the area of 690 km2, but their locations were slightly different from that in summer 2007. So, we found about 1 active sett per 100 km2 and 1.9 inds per 100 km2. In the seven active setts found we revealed the following inhabitants: (1) 2 adults; (2) 2 adults; (3) 1 adult; (4) 1 adult; (5) 1 adult; (6) 2 adults, 2 cubs; (7) 2 adults. Only one out of seven active setts held litters (14.3 %). Approximate portion of juveniles was 15.3 %.
In summer 2009 there we censused 5 active setts on the area of 690 km2 only, i.e. about 0.7 active sett per 100 km2 and 0.7 inds per 100 km2. In all five active setts we found solitary adult individuals only. No litter in the setts was revealed.
These density estimates clearly indicate a severe decline of the badger population in Naliboki Forest. In the 2000s we found, on average, only one active sett per 100 km² and 1.9 individuals per 100 km² in otherwise fairly favourable habitats.
For comparison, at a similar latitude in Scotland, badger population density ranges from 1 to 8 individuals per km² (mean 2.2). There, the average family group consists of 5.4 adults (range 2–11) (Kruuk & Parish, 1982). In contrast, in Naliboki Forest in the 2000s, solitary individuals dominated sett occupancy: 52.6% of active setts were inhabited by lone badgers. Moreover, Kruuk (1989) reported that in Scotland 81.3% of active setts contained litters (13 litters out of 16 family groups), whereas in Naliboki Forest in the 2000s only about 16% of active setts held litters.
In recent decades, poaching of badgers in Naliboki Forest has become rare, suggesting that the strong decline observed in the 2000s and earlier was driven primarily by natural factors. Based on data from Naliboki Forest and comparable information from other regions of Belarus – particularly Paazierre Forest – we developed several hypotheses regarding non‑anthropogenic causes of the decline and gradually confirmed them (Rotenko & Sidorovich, 2017). Below we summarise the findings on the causes of the badger population decline, which turned out to be fairly complex.
To clarify the following complex explanations, we would like to state at the outset that the recent decline of the badger population was driven primarily by the multi‑faceted impact of the naturalized raccoon dog. Many additional factors either amplified the raccoon dog’s influence or directly exacerbated the decline of badgers. We begin with the mechanisms through which the raccoon dog population negatively affects badgers.
During the harsh winter conditions that were typical across Belarus – including Naliboki Forest – at least until the late 2000s, badgers entered a deep, prolonged sleep. Raccoon dogs, however, often overwintered in the same setts and tended to become active periodically during thaws. While sharing the sett, raccoon dogs frequently attempted to isolate themselves from the sleeping badgers by blocking underground tunnels with soil. When this occurred, badgers could become sealed inside their sleeping chambers and die from suffocation. In the 2000s and earlier, approximately 10% of badgers died annually in this way.
A second major negative influence of raccoon dogs was linked to several interacting ecological factors:
- the harshness and long duration of winters,
- relatively low biomass of earthworms in dry‑land habitats,
- and the presence of large predators such as wolves and lynxes.
Badgers tend to avoid areas with high predation risk from these large carnivores. As a result, they usually move directly between their main sett and outlier burrows, which are located mostly in dry‑land habitats (Sidorovich et al., 2011; Rotenko & Sidorovich, 2017). This movement pattern limits their access to black alder swamps, where earthworm biomass is relatively high and would otherwise provide an important food source.
Under such conditions, the only viable feeding strategy for badgers was scavenging and generalist predation on small prey. This diet likely did not allow them to accumulate sufficient fat reserves for the long winter sleep that remained typical until the mid‑2010s. By early March, many badgers had exhausted their fat stores and were forced to forage frequently in the still‑snowy forest for about a month.
During this period, carrion – mostly from ungulates that died over winter – was the only substantial food source. However, raccoon dogs, which wake up at least a month earlier than badgers, had already consumed most of the available carrion, especially around badger setts. In this competition, badgers were heavily outcompeted and often left with almost no suitable food.
Consequently, badgers were forced to scavenge for poor‑quality items and frequently experienced starvation. In winters that lasted particularly long, it was not uncommon for a portion of the badger population to die from starvation.
The third major impact of raccoon dogs on badgers was the likely influence of diseases associated with the dense population of this alien species. Frequent presence of raccoon dogs in badger setts, combined with their high local density, created highly favourable conditions for disease circulation. In such circumstances, badgers – who spend the majority of their time inside setts – were affected much more severely than raccoon dogs.
By the 2000s and earlier, under the combined pressure of raccoon dogs and other unfavourable factors (see below), most badger setts in Belarus were occupied by solitary individuals. This situation made it difficult for adult females to mate successfully. Even when a solitary female did become pregnant, raising a litter alone was extremely challenging. Badgers are a social species, and one of their key social traits is alloparental behaviour (Woodroffe, 1993). When living alone or in very small groups, cubs were left unattended during the mother’s foraging trips. During time, when the mother is absent, cubs can be attacked by other burrowing carnivores – particularly red foxes or raccoon dogs – which frequently bred in the same sett or in nearby outliers. This constituted the fourth major impact of raccoon dogs on badgers.
When most badgers lived alone, finding a mate required travelling far beyond the relatively safe routes between the main sett and outliers. Especially males had to move long distances during the mating season. Inevitably, such movements exposed them to predation by wolves and lynxes. As a result, badger population density declined further, and the number of adult males became extremely low – often only 1–2 males per 10 adult females. This imbalance further impaired breeding success. Again, it was the multi‑layered impact of raccoon dogs that initiated this deterioration in badger reproduction.
In addition to these direct and indirect effects of raccoon dogs, badgers were still killed by poachers, and their setts were destroyed by heavy modern forestry machinery, causing sleeping badgers to suffocate. However, in the 2000s and earlier, this human impact was not the primary driver of decline compared to the negative influence of raccoon dogs.
Since the early 2000s, the raccoon dog population in Naliboki Forest and its rural surroundings began to decline. Such declines occurred periodically (Rotenko & Sidorovich, 2017). The main cause was an extremely high infestation with the helminth Alaria alata. Raccoon dogs heavily affected by this parasite also became highly susceptible to mange, which further deepened the population depression. During these declining phases, raccoon dogs reproduced very weakly.
In the winters of 2003-2004 in Naliboki Forest on average the raccoon dog population density was assessed as 6.8 individuals per 10 km². The population decline of the raccoon dog in Naliboki Forest seemingly lasted until 2010. Some recovery in raccoon dogs started in early 2010s, but soon after, number of raccoon dogs decreased considerably (6-10 fold) again due to they were nearly exterminated with the heavy predation of wolves and lynxes. These predators, being common in Naliboki Forest, appeared in the conditions of sharply reduced supply with relevant prey after the population crash in roe deer in March-April 2013 and that in wild boars during March-September 2013. During intensive studies on raccoon dogs in autumn 2014 we registered few families only. Perhaps, the species population density became one breeding pair per 10-30 km².
However, as shown by the badger census data from 2007–2009 (see above), a reduced number of raccoon dogs was not sufficient to trigger a rapid recovery of the badger population. The restoration of the badger population takes time and actually began only about a decade after the initial decline of raccoon dogs.
In summer 2012, we recorded approximately 9.6 badgers (3.7 active setts) per 100 km², compared to only 0.7 in 2009. That year, 14 of the 30 active main setts (46.7%) contained litters. In 2011, the same area held about 5.5 badgers (2.3 active setts) per 100 km², with 7 of 17 active setts (41.2%) containing litters.
In 2012, local densities varied markedly. In an 80 km² area near Vialikaja Chapun’ village, four active setts held 19 badgers – 23.8 individuals per 100 km². Meanwhile, in the central part of Naliboki Forest, where habitat carrying capacity is relatively low, density remained very low at about 2.6 individuals per 100 km².
After 2012, we discontinued terrain‑wide monitoring of the badger population. Since 2016 our 10–15 camera traps have monitored model setts almost year‑round. Despite the limited dataset, several clear changes in the badger population have become evident.
Today, badgers in Naliboki Forest have largely escaped the former impacts of raccoon dogs. Two major processes explain this shift:
- Raccoon dogs have become relatively rare, especially since 2015, due to, being in the stage of population decline (Rotenko & Sidorovich, 2017), they were heavily predation by lynxes and wolves. Numerous lynxes in particular suppressed raccoon dog reproduction by killing almost all cubs. In recent years, raccoon dogs have essentially ceased reproducing in Naliboki Forest.
- Winters have become markedly milder and nearly twice as short, likely due to climate change. During these milder winters, badgers remain intermittently active and are able to expel raccoon dogs from overwintering burrows. As a result, the risk of being blocked and suffocated by raccoon dogs has become extremely low.
Consequently, since 2015 the badger has become a common species in Naliboki Forest, with an average density of about 30 individuals per 100 km². As before, densities are higher in the south‑western half of the forest (approximately 30–50 individuals per 100 km²) and lower in the north‑eastern half (10–30 individuals per 100 km²).
Badgers in Naliboki Forest have benefited greatly from the presence of numerous wolves and lynxes, because these predators keep the density of the local raccoon dog population very low. At the same time, wolves and especially lynxes do kill badgers as well. However, the net effect of their presence is strongly positive for badgers. As a result, the species thrived in Naliboki Forest at least during 2015–2019.
Camera‑trap monitoring at model badger setts shows that lynxes visit these setts almost year‑round. During periods when badgers are highly active, lynxes often watch them from ambush positions – lying or sitting close to the burrow entrances. Some impatient lynxes even attempt to enter the sett to scare badgers out. The frequency of lynx visits to a particular sett clearly correlates with the presence of cubs and with the total number of badgers living there, i.e. with the availability of potential prey.
Wolves show a different pattern. They mostly visit badger setts during their own denning period. When a sett contains many badgers, wolf breeders usually do not attempt to kill them in order to take over the sett – it would require too much effort during an already demanding time. However, a solitary badger may be deliberately killed by wolf breeders so that the sett can be occupied for denning. In some cases, badgers abandon their sett in May when wolves begin to den there.
Breeding female lynxes show a similar pattern of denning behaviour in badger setts. In large setts composed of several unconnected parts, badgers and a breeding female lynx may even coexist relatively peacefully, each using different sections of the sett.
Zoology by Vadim Sidorovich 